--- title: "Dormer vs Velux Loft Conversion: Which Is Right? | J&Co" description: "Dormer vs Velux loft conversion comparison — cost, space added, planning rules, head height and resale value. Honest 2026 guidance from a Hertfordshire builder." lang: en-GB json-ld: | [ { "@context": "https://schema.org", "@type": "Article", "headline": "Dormer vs Velux Loft Conversion: Which Is Right for You?", "description": "Dormer vs Velux loft conversion comparison — cost, space added, planning rules, head height and resale value. Honest 2026 guidance from a Hertfordshire builder.", "mainEntityOfPage": "https://jandco-contractorsltd.co.uk/guides/dormer-vs-velux-loft-conversions/", "datePublished": "2026-05-07", "dateModified": "2026-05-07", "author": { "@type": "Person", "name": "Jamie Pocock", "jobTitle": "Owner & Lead Contractor", "worksFor": { "@id": "https://jandco-contractorsltd.co.uk/#business" } }, "publisher": { "@type": "Organization", "name": "J&Co Contractors", "url": "https://jandco-contractorsltd.co.uk" }, "image": [ "https://jandco-contractorsltd.co.uk/assets/wa-435-79-Cfvt7K6N.jpeg" ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Can I have both Velux and a dormer?", "acceptedAnswer": { "@type": "Answer", "text": "Yes — a typical rear dormer plus 2 Velux on the front slope is one of our most common designs. It gives full standing height across the rear (where the bedroom and bathroom go) and natural light from the front slope. Best of both for most layouts." } }, { "@type": "Question", "name": "Will a dormer make my house ugly from outside?", "acceptedAnswer": { "@type": "Answer", "text": "A well-designed dormer matches the existing roof tile, has appropriate proportions, and uses lead or zinc cheeks for visual coherence. Done properly it looks intentional. Done badly it looks bolted-on. Architect input on the front elevation matters." } }, { "@type": "Question", "name": "Is a Velux conversion strong enough for a bedroom?", "acceptedAnswer": { "@type": "Answer", "text": "Yes — both Velux and dormer conversions involve full structural floor design (new joists, often steel beams to support them) and meet Building Control floor-loading requirements. The conversion type doesn't affect structural integrity." } }, { "@type": "Question", "name": "Can I do an en-suite in a Velux conversion?", "acceptedAnswer": { "@type": "Answer", "text": "Often yes, but tight — the bathroom usually has to sit on one side of the apex with a sloping ceiling. Dormer conversions accommodate full standing-height bathrooms much more easily and are the better choice if en-suite is essential." } }, { "@type": "Question", "name": "How disruptive is each type?", "acceptedAnswer": { "@type": "Answer", "text": "Velux: less disruptive, no exterior scaffold for the entire build, faster completion. Dormer: more disruptive (full scaffold, dormer-cut day involves opening the roof), but only by 1–2 weeks of additional inconvenience for substantially more space." } }, { "@type": "Question", "name": "Which type do most Hertfordshire homeowners choose?", "acceptedAnswer": { "@type": "Answer", "text": "Roughly 60% of our loft conversions are dormer (rear, often combined with hip-to-gable on detached homes), 25% are Velux, 15% are hip-to-gable plus dormer or mansard. The dormer's value uplift and usable space win out for most families when budget allows." } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://jandco-contractorsltd.co.uk/" }, { "@type": "ListItem", "position": 2, "name": "Building & Construction", "item": "https://jandco-contractorsltd.co.uk/building-construction/" }, { "@type": "ListItem", "position": 3, "name": "Loft Conversions", "item": "https://jandco-contractorsltd.co.uk/loft-conversions/" }, { "@type": "ListItem", "position": 4, "name": "Dormer vs Velux Loft Conversion: Which Is Right for You?", "item": "https://jandco-contractorsltd.co.uk/guides/dormer-vs-velux-loft-conversions/" } ] } ] --- We use essential cookies to run this site, and optional cookies only with your consent. [Cookie policy](/cookie-policy/) AcceptReject Open 7 days · Hours vary by day · 25 years' experience [Office: 01279 216 215](tel:01279216215) | [Mobile: 07379 964569](tel:07379964569) [![J&Co Contractors logo](/assets/jandco-logo-DkXiFtbE.png)](/) Services Areas [About](/about/) [Our Work](/our-work/) [Blog](/blog/) [Reviews](/reviews/) [Contact](/contact/) [01279 216 215](tel:01279216215) [Free Quote](/contact/) 1. [Home](/) 2. [Building & Construction](/building-construction/) 3. [Loft Conversions](/loft-conversions/) 4. Dormer vs Velux Loft Conversion: Which Is Right for You? Guide · Loft Conversions # Dormer vs Velux Loft Conversion: Which Is Right for You? Velux is cheaper, faster and usually doesn't need planning. Dormer adds significantly more usable head height and floor area. Here's how to choose between the two on real budgets and real roofs. Last updated: May 2026 · By Jamie Pocock Quick Answer **Choose Velux if you have 2.2m+ existing apex height, want to spend £30,000–£45,000, and need the conversion finished in 6 weeks.** Choose dormer (£45,000–£65,000, 8–10 weeks) if you want a usable double bedroom rather than a single, need a bathroom upstairs, or have under 2.2m apex height. Dormer adds 30–50% more usable floor area — almost always worth the extra cost if the budget supports it. ![Side-by-side comparison of dormer and Velux loft conversion options on a Hertfordshire roof](/assets/wa-435-79-Cfvt7K6N.jpeg) ## What each type physically does to the roof ### Velux conversion The roof line stays untouched. Velux skylight windows are cut into the existing slope to bring light in. Floor is laid, walls and ceilings insulated and lined, stairs installed, electrics and heating run. The internal space is the existing loft volume — sloping ceilings on both sides, full standing height only at the apex. ### Dormer conversion A box-shaped extension is built outward from the rear (or side) slope of the roof, creating a vertical wall, vertical sides, and a flat or pitched roof. Inside the dormer, you have full standing height across the entire dormer floor area — typically doubling the usable space compared to a Velux on the same roof. ## Space gained — the real difference On a typical 7m × 4m loft footprint with a 35° pitch: - **Velux:** usable floor area (1.5m+ head height) ~12–15m². Bedroom that fits a double bed but wardrobes have to sit under the slopes. - **Dormer (rear, full-width):** usable floor area ~22–28m². Room for double bed, full-height wardrobes, en-suite, sometimes a desk area. The dormer roughly doubles the usable space. For most families, that's the difference between a single guest room and a master bedroom suite. ## Cost difference and break-even Typical 2026 figures: Velux £30,000–£45,000, dormer £45,000–£65,000. The dormer costs roughly £15,000–£20,000 more for roughly twice the usable space. Cost per usable m² actually drops significantly with the dormer. Property value uplift varies too. In Hertfordshire and Essex, a Velux conversion typically adds 8–12% to value; a dormer conversion typically adds 15–20%. The dormer pays back its incremental cost faster at sale than the Velux. Full pricing detail in our [loft conversion cost guide](/guides/loft-conversion-cost-uk/). ## Planning permission Both can often be done under Permitted Development on most semi-detached and detached houses, subject to volume limits (40m³ for terraced, 50m³ for semi/detached). Larger dormers, side dormers and any conversion in conservation areas, on listed buildings, or in Article 4 zones need full planning permission. Velux conversions almost always fall within PD. Dormers sometimes exceed PD volume limits — design carefully to stay within them where possible, or accept the planning timeline (typically 8–12 weeks) and £258 application fee. ## Direct comparison Factor Velux Dormer Cost (2026) £30,000–£45,000 £45,000–£65,000 Build time 5–7 weeks 8–10 weeks Usable floor area 12–18 m² 22–32 m² Standing height (full) Apex only Full dormer area Bathroom feasible? Tight, sometimes no Yes, comfortably Planning Usually PD Often PD, sometimes planning External roof appearance Unchanged Visible from rear/side Property value uplift 8–12% 15–20% ## Other things that influence the choice **Existing apex height.** Below 2.2m at the apex, Velux conversions are tight. Below 1.9m, they don't really work as habitable rooms. A dormer effectively raises the ceiling across the dormer footprint and rescues low-pitched lofts that wouldn't be liveable as Velux conversions. **Front of house vs rear.** Front-facing dormers usually need full planning permission and conservation officers often resist them on visual grounds. Rear-facing dormers are nearly always achievable and rarely controversial. Side dormers depend on the street context and party-wall position. **Property type.** Mid-terrace houses are limited to 40m³ under PD (versus 50m³ for semis and detached). That often constrains the dormer size. Bungalow loft conversions are nearly always dormer or hip-to-gable because the apex height is rarely sufficient for Velux. **Resale market signal.** Estate agents in Hertfordshire and Essex consistently price dormer conversions higher per m² than Velux conversions, even controlling for total floor area. Buyers value the full standing height and en-suite feasibility. **Future extension plans.** If you're also planning a rear extension later, the dormer should be designed in coordination — roof line, rainwater goods and finishes need to flow together. Plan once, not twice. ![Recently completed roofing project by J&Co Contractors in Hertfordshire](/assets/wa-435-169-BMBPQKLs.jpeg) About the Author ## Jamie Pocock — Owner & Lead Contractor Jamie has 25 years' hands-on experience in roofing and building across Hertfordshire and Essex. He runs every J&Co Contractors project personally — from quote to completion — and writes these guides from real on-the-tools knowledge of what works, what doesn't, and what costs what in 2026. - 25 years' hands-on roofing and building experience - CRC Certified Roofer — self-certifies under Building Regs - SafeContractor approved - Written completion sign-off on every job FAQs ## Frequently asked questions ### Can I have both Velux and a dormer? ### Will a dormer make my house ugly from outside? ### Is a Velux conversion strong enough for a bedroom? ### Can I do an en-suite in a Velux conversion? ### How disruptive is each type? ### Which type do most Hertfordshire homeowners choose? Related Guides [Loft conversion cost UK 2026](/guides/loft-conversion-cost-uk/) [Single vs double-storey extensions](/guides/single-vs-double-storey-extensions/) [Back to Loft Conversions](/loft-conversions/) ## Not sure whether dormer or Velux is right for your loft? We'll survey your roof, talk through what's achievable under PD, and quote both options where they're both viable. No hard sell — the right answer is whatever genuinely suits your roof and budget. [See our loft conversions service](/loft-conversions/) [01279 216 215](tel:01279216215) Page last updated: May 2026 · J&Co Builders Ltd · 1 Ugley Hall Cottages, Bishop's Stortford CM22 6JB ![J&Co Contractors](/assets/jandco-logo-DkXiFtbE.png) Owner-led roofing and building contractors covering Bishop's Stortford, Hertfordshire and Essex. 25 years of hands-on trade experience. Open seven days. 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